Thoughts on the Nature of Stress

​I've been thinking a lot lately about stress. In doing so I recalled an occasion from many years ago when a dendrologist from the U​.​S​.​ Forest Service came to the Arboretum and expressed interest in seeing the bonsai collection. This was before the bonsai garden was built, so I walked the man through the hoop house to look at the little trees. I was eager to solicit his opinion. As an educated plant expert and a forestry professional with first-hand working knowledge of trees far beyond what most people have, this person's perspective would naturally be different. He professed to have no prior knowledge of bonsai, so I was curious to know what he thought about what he was now seeing. I asked him outright. "It's amazing," he said, "that you're able to keep them so healthy when they're under so much stress."

It is interesting how we will sometimes hear only part of something said. The dendrologist had complimented the health of the plants, but all I heard was the part about them being "under so much stress​.​" I responded with some degree of defensiveness: "These trees are very well cared for! What makes you say they're under a lot of stress?" He looked at me a little surprised but smiled kindly and said, "Oh, I can see you take good care of them. But they are under stress because they're growing in containers, and you must prune them often to keep them so small. I see wires on some of them, which I'm guessing has something to do with shaping them, and all of that is stressful to the plant." It was an eye​-​opening moment. I had never thought of the techniques used to train bonsai as being a form of stress. When I considered, though, how trees would normally grow out in nature, I could see how different it was for a tree cultivated as a bonsai, and I could understand how those differences could be construed as stressful. The walls of a container constrain the outward reach of roots and cause them to behave differently than they would if they were growing in the earth. The pruning represents a constant taking from the plant, hindering it in its effort to grow outward and upward toward the sun. The wiring, indeed a tool for shaping, forces the plant to grow in a pattern different from that which it is inclined to do. ​​Any given tree in nature follows a path of development toward an objective — being well rooted in the earth and stretching itself upward as much as possible to access sunlight, so it can photosynthesize and feed itself and stay alive, ultimately enabling it to reach maturity and reproduce and pass along its genetic information. That's the game plan. All obstructions to achieving this goal frustrate the plant in its efforts to do what nature requires of it. When you are frustrated in your efforts to do something you need to do, it's stressful.

Is stress bad? It depends. Too much stress is certainly bad, because it can result in the failure of a system. Put too much stress on an arm, for example, and some part of it will likely rupture or break, and then the arm won't be able to do what an arm is supposed to do. The arm may eventually recover from the stress​-​induced damage, but it may well exhibit some lasting evidence of the event, even to the point of never again functioning as well. However​ ​some degree of stress is useful or even beneficial. Picture the arm of a bodybuilder, sculpted with powerful muscle. That muscle tissue was built by subjecting it to repeated, controlled stress, usually in the form of lifting and moving a heavy weight, such as curling a dumbbell. As long as a threshold of tolerance is not exceeded — too much weight, too many repetitions — the bodybuilder's arm will gradually increase in strength as it builds capacity for the action it is being called upon to perform. It responds to the stress applied to it in a way we identify as positive. Now picture the arm of a sickly and bedridden person. Such an arm receives little or no stress because the person to whom it belongs is not able to use it for much, and so the muscles in it atrophy. In this instance the lack of stress, which we might reflexively be inclined to think is a desirable condition, produces a negative outcome. Most of us are neither bodybuilders nor bedridden. Our arms are not bulging with muscle, nor are they spindly and stick-like​; they are somewhere in between. The degree to which our muscles are developed or undeveloped is a reflection of how much stress they are called upon to operate under. Stress is not inherently bad or good, but rather an elemental aspect of our existence with which we have little choice but to engage.

That long ago conversation with the visiting dendrologist was critically important to me. Not only did it change the way I think about bonsai training, it caused me to look at trees in nature in a new light. Trees, like human beings and all the rest of organic life, are not only subject to stress but are actually shaped by it. Instead of picturing an arm, think now of a tree limb. A big, powerful, undulating tree limb is the product of a life of stress ​— the stress of reaching out to hold its leaves in position to access sunlight, and to hold them that way despite their weight and the weight of the limb itself against the force of gravity. The limb holds that weight out as far as it can while the tempest winds blow, or when rain adds untold water weight to the leaves, or when the snow and ice accumulate, and it does so year after year for decades, or centuries. Sometimes the stress is too great and the limb breaks. When it does the tree as a living organism must deal with the stress of a wound that is open to the advances of pathogens and wood-eating insects, as well as the loss of capacity due to the removal of so much of its photosynthetic material. Other sources of stress commonly faced by trees include flooding, drought, fire, competition for space and resources, interaction with humans, and changing environmental conditions. Stresses both large and small work incessantly on trees, and the trees' responses to these ​stressors ​manifest themselves physically.

A tree grown as a bonsai is also subject to a life of stress, some of which is the same as that which trees in nature endure. Fungal disease, boring insects and hurricanes do not differentiate between bonsai and trees in the landscape. Humans offer some protection to the bonsai they grow: sheltering them from environmental extremes, monitoring them for problems and responding as necessary, fertilizing them and keeping them correctly watered. But bonsai growers also induce stress intentionally as a means of creating the look we find desirable in our miniature trees. We take our trees out of the earth and grow them in a fabricated medium, in containers. In doing that we are also removing them from their natural communal context and to some extent isolating them. We prune them regularly, limiting their ability to grow larger by taking away not only leaves and stems but also roots. We wrap them in wire so we can bend and twist them into different shapes. If we do all these activities carefully, intelligently, the tree will usually endure and the end result of all the stress will be a thing of beauty. If we do too much, causing too much stress, the end result will be an unhealthy or dead tree — a failed system.

“If we do all these activities carefully, intelligently, the tree will usually endure and the end result of all the stress will be a thing of beauty.”

This is why, when the dendrologist visitor offered his opinion he was actually being complimentary. He saw the bonsai as trees and he recognized the stress to which they were subjected, but he also recognized that the trees were not suffering for it. They were under stress but they were healthy. That is, they were meeting the challenge of the stress and carrying on as fully functioning systems.

As I said, I have been thinking a lot lately about stress, because I'm feeling it right now. This Saturday is World Bonsai Day, the day by which the Arboretum's bonsai are promised to be back out on display in the bonsai garden. Getting to that point is a big job, with more to it than most folks might imagine, coming at what is the most busy time of year anyway, and I'm feeling the pressure of demand and expectation. No, it's not the kind of stress experienced by citizens of a city under attack in a country at war, or the workers at a hospital dealing with a surge of patients during a pandemic. I am very grateful for that. Those are examples of traumatic stress, the kind that causes system failure. Our hearts go out to the people who struggle to bear up under that level of pressure. The kind of stress I'm feeling now is more of a garden variety, the sort that invites you to grow by posing a challenge. It's a good sort of stress, one I take on willingly, but it is stressful nonetheless!

I hope those of you who can will come out to the Arboretum this weekend and see the bonsai back out on their benches, fresh in their new foliage and presented for your enjoyment. For those of you who cannot make it, next week's entry will have lots of pictures.